What is availability?
Actually, a simple question but the answer is very complex. So, in turn, look into the following approaches.
First approach
Availability is the ratio of time within an agreed period in which the system is operational for its actual purpose (operation time) at the agreed time.
The operating time may be limited by:
- Planned maintenance
- Unplanned maintenance
- Error
- Damage
- Repair time to eliminate errors and damage
The measure of availability is usually given as a percentage.
Second approach
Alternatively, availability is also defined as the proportion of available objects (services) in the total number of objects (services). In summary, availability is thus a quality criterion and a measure for a system, subsystem, service, and so on. So, now you know what availability means. In the following sections, we will concentrate on the first approach presented.
